Three dimensional (3D) printers are in rapidly increasing use. One class of 3D printers includes stereolithography printers having a general principle of operation including the selective curing and hardening of radiation curable (photocurable) liquid resins. A typical stereolithography system includes a resin vessel holding the photocurable resin, a movement mechanism coupled to a support surface, and a controllable light engine. The stereolithography system forms a three dimensional (3D) article of manufacture by selectively curing layers of the photocurable resin. Each selectively cured layer is formed at a “build plane” within the resin.
One challenge with stereolithography systems is an optical path variation across the build plane that arises due to deformation and wear of certain portions of the resin vessel. What is needed is a way of assuring that the optical path remains dimensionally accurate even after repeated fabrication of three dimensional (3D) articles of manufacture.